Strain-induced topological phase transitions in HgTe

Mercury telluride is a known semi-metal in its bulk zinc-blende structure with electronic bandgap Eg $\sim$ -0.3 eV and has been predicted to be a topological insulator under strain. In this study, we carried out ab intio electronic structure calculations to investigate the transition of HgTe system from semi-metal into the topological insulating phase under compressive strain along [001], [110] and [111] directions. The compressive strains along these directions close and reopen a gap at the $\Gamma$ point and topological phase is emerged. We will discuss the evolution of topological insulator phase in the context of semimetal nature of bulk HgTe system.